constructive processes that build mountains simple

The supercontinent of Pangaea formed as the landmasses gradually combined roughly between 300 and 100 mya. They have gradually moved over the course of hundreds of millions of years-alternately combining into supercontinents and pulling apart in a process known as continental drift. The locations of Earth’s major landmasses today are very different from their locations in the past (Fig. The earth has changed in many ways since it first formed 4.5 billion years ago. Images courtesy of United States Geological Survey ( USGS) The motion of plates can be described in four general patterns: Other observable results of short-term plate movement include the gradual widening of the Great Rift lakes in eastern Africa and the rising of the Himalayan Mountain range. Most of the earthquakes and volcanoes around the Pacific ocean basin-a pattern known as the “ring of fire”-are due to the movement of tectonic plates in this region. The term fault is used to describe the boundary between tectonic plates. Earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. The upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.Įach tectonic plate is free-floating and can move independently.

Both types of crust rest atop solid, upper mantle material. It is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. Recall that the crust is the solid, rocky, outer shell of the planet. The earth’s crust is broken into separate pieces called tectonic plates (Fig.

Image courtesy of United States Geological Survey ( USGS)

Constructive processes that build mountains simple